Many people wrote in about our brief mention last week in TidBITS #227 of some kind of video on demand (VOD) service in Britain related to Apple's rumored set-top boxes. Almost everyone had a different take on the situation, but as near as I can tell, here's the story:

BT (which prefers to be called BT, not British Telecom) is a phone company that wants to offer more than just phone service, in order to better compete with the many cable companies springing up. BT is trying to jump through a loophole in the law that prohibits them from broadcasting over their twisted pair copper (and some fiber optic) network by doing "monocasting," where subscribers request movies and TV shows and then receive the programming over their existing phone lines. According to rumor, the programming comes from the BBC.

According to a source at BT and to an article in the Feb-94 issue of UK MacUser, BT is currently conducting a technical trial that involves about 65 employees in the Ipswich, Suffolk area. Each employee's home television is attached to an LC III-based Macintosh set-top box, which contains a special MPEG card for handling video transmission. Although the box does not come with a keyboard or screen, users can request, pause, rewind, fast forward, and freeze programs.

BT is distributing the VHS-quality video using an Oracle Media Server running on massively parallel nCube hardware. The video travels over the copper twisted pair phone lines using a compression technology called ADSL (Asymetrical Digital Compression Line, and I'm not sure why the acronym doesn't work out). The technology allows BT to send video out at several megabits per second and for users to send information back at several hundred kilobits per second. Evidently, even while a house receives video, someone at the house can make a phone call over the same wires. The technology is apparently just beginning to work; unfortunately, nobody participating in the test wrote in, so I don't know how well it works.

BT's future plans are a bit murkier, but the company does have plans for a second technical trial, which will involve hundreds or even thousands of users. For the second trial, BT may use their twisted copper network, may try to use ISDN, and may include home shopping and banking services. Evidently, Apple plans to continue testing set-top boxes, with the eventual goal of coming out with a commercial product.

You can find additional information in the May and June issues of Australian Communications, which contain a two-part article about DMT ADSL and on the results of the MPEG Test Group's recent subjective viewing tests. For those who read Norwegian, there's a Web page at the Norwegian Telecom Research Institute that reportedly talks about video on demand projects in Norway and Europe.